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linux/kernel/time.c

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/*
* linux/kernel/time.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* This file contains the interface functions for the various
* time related system calls: time, stime, gettimeofday, settimeofday,
* adjtime
*/
/*
* Modification history kernel/time.c
*
* 1993-09-02 Philip Gladstone
* Created file with time related functions from sched.c and adjtimex()
* 1993-10-08 Torsten Duwe
* adjtime interface update and CMOS clock write code
* 1995-08-13 Torsten Duwe
* kernel PLL updated to 1994-12-13 specs (rfc-1589)
* 1999-01-16 Ulrich Windl
* Introduced error checking for many cases in adjtimex().
* Updated NTP code according to technical memorandum Jan '96
* "A Kernel Model for Precision Timekeeping" by Dave Mills
* Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10)
* (Even though the technical memorandum forbids it)
* 2004-07-14 Christoph Lameter
* Added getnstimeofday to allow the posix timer functions to return
* with nanosecond accuracy
*/
#include <linux/module.h>
#include <linux/timex.h>
#include <linux/errno.h>
#include <linux/smp_lock.h>
#include <linux/syscalls.h>
#include <linux/security.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
/*
* The timezone where the local system is located. Used as a default by some
* programs who obtain this value by using gettimeofday.
*/
struct timezone sys_tz;
EXPORT_SYMBOL(sys_tz);
#ifdef __ARCH_WANT_SYS_TIME
/*
* sys_time() can be implemented in user-level using
* sys_gettimeofday(). Is this for backwards compatibility? If so,
* why not move it into the appropriate arch directory (for those
* architectures that need it).
*/
asmlinkage long sys_time(time_t __user * tloc)
{
time_t i;
struct timeval tv;
do_gettimeofday(&tv);
i = tv.tv_sec;
if (tloc) {
if (put_user(i,tloc))
i = -EFAULT;
}
return i;
}
/*
* sys_stime() can be implemented in user-level using
* sys_settimeofday(). Is this for backwards compatibility? If so,
* why not move it into the appropriate arch directory (for those
* architectures that need it).
*/
asmlinkage long sys_stime(time_t __user *tptr)
{
struct timespec tv;
int err;
if (get_user(tv.tv_sec, tptr))
return -EFAULT;
tv.tv_nsec = 0;
err = security_settime(&tv, NULL);
if (err)
return err;
do_settimeofday(&tv);
return 0;
}
#endif /* __ARCH_WANT_SYS_TIME */
asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
{
if (likely(tv != NULL)) {
struct timeval ktv;
do_gettimeofday(&ktv);
if (copy_to_user(tv, &ktv, sizeof(ktv)))
return -EFAULT;
}
if (unlikely(tz != NULL)) {
if (copy_to_user(tz, &sys_tz, sizeof(sys_tz)))
return -EFAULT;
}
return 0;
}
/*
* Adjust the time obtained from the CMOS to be UTC time instead of
* local time.
*
* This is ugly, but preferable to the alternatives. Otherwise we
* would either need to write a program to do it in /etc/rc (and risk
* confusion if the program gets run more than once; it would also be
* hard to make the program warp the clock precisely n hours) or
* compile in the timezone information into the kernel. Bad, bad....
*
* - TYT, 1992-01-01
*
* The best thing to do is to keep the CMOS clock in universal time (UTC)
* as real UNIX machines always do it. This avoids all headaches about
* daylight saving times and warping kernel clocks.
*/
inline static void warp_clock(void)
{
write_seqlock_irq(&xtime_lock);
wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
xtime.tv_sec += sys_tz.tz_minuteswest * 60;
time_interpolator_reset();
write_sequnlock_irq(&xtime_lock);
clock_was_set();
}
/*
* In case for some reason the CMOS clock has not already been running
* in UTC, but in some local time: The first time we set the timezone,
* we will warp the clock so that it is ticking UTC time instead of
* local time. Presumably, if someone is setting the timezone then we
* are running in an environment where the programs understand about
* timezones. This should be done at boot time in the /etc/rc script,
* as soon as possible, so that the clock can be set right. Otherwise,
* various programs will get confused when the clock gets warped.
*/
int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
{
static int firsttime = 1;
int error = 0;
error = security_settime(tv, tz);
if (error)
return error;
if (tz) {
/* SMP safe, global irq locking makes it work. */
sys_tz = *tz;
if (firsttime) {
firsttime = 0;
if (!tv)
warp_clock();
}
}
if (tv)
{
/* SMP safe, again the code in arch/foo/time.c should
* globally block out interrupts when it runs.
*/
return do_settimeofday(tv);
}
return 0;
}
asmlinkage long sys_settimeofday(struct timeval __user *tv,
struct timezone __user *tz)
{
struct timeval user_tv;
struct timespec new_ts;
struct timezone new_tz;
if (tv) {
if (copy_from_user(&user_tv, tv, sizeof(*tv)))
return -EFAULT;
new_ts.tv_sec = user_tv.tv_sec;
new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC;
}
if (tz) {
if (copy_from_user(&new_tz, tz, sizeof(*tz)))
return -EFAULT;
}
return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
}
long pps_offset; /* pps time offset (us) */
long pps_jitter = MAXTIME; /* time dispersion (jitter) (us) */
long pps_freq; /* frequency offset (scaled ppm) */
long pps_stabil = MAXFREQ; /* frequency dispersion (scaled ppm) */
long pps_valid = PPS_VALID; /* pps signal watchdog counter */
int pps_shift = PPS_SHIFT; /* interval duration (s) (shift) */
long pps_jitcnt; /* jitter limit exceeded */
long pps_calcnt; /* calibration intervals */
long pps_errcnt; /* calibration errors */
long pps_stbcnt; /* stability limit exceeded */
/* hook for a loadable hardpps kernel module */
void (*hardpps_ptr)(struct timeval *);
/* we call this to notify the arch when the clock is being
* controlled. If no such arch routine, do nothing.
*/
void __attribute__ ((weak)) notify_arch_cmos_timer(void)
{
return;
}
/* adjtimex mainly allows reading (and writing, if superuser) of
* kernel time-keeping variables. used by xntpd.
*/
int do_adjtimex(struct timex *txc)
{
long ltemp, mtemp, save_adjust;
int result;
/* In order to modify anything, you gotta be super-user! */
if (txc->modes && !capable(CAP_SYS_TIME))
return -EPERM;
/* Now we validate the data before disabling interrupts */
if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
/* singleshot must not be used with any other mode bits */
if (txc->modes != ADJ_OFFSET_SINGLESHOT)
return -EINVAL;
if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
/* adjustment Offset limited to +- .512 seconds */
if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE )
return -EINVAL;
/* if the quartz is off by more than 10% something is VERY wrong ! */
if (txc->modes & ADJ_TICK)
if (txc->tick < 900000/USER_HZ ||
txc->tick > 1100000/USER_HZ)
return -EINVAL;
write_seqlock_irq(&xtime_lock);
result = time_state; /* mostly `TIME_OK' */
/* Save for later - semantics of adjtime is to return old value */
save_adjust = time_next_adjust ? time_next_adjust : time_adjust;
#if 0 /* STA_CLOCKERR is never set yet */
time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */
#endif
/* If there are input parameters, then process them */
if (txc->modes)
{
if (txc->modes & ADJ_STATUS) /* only set allowed bits */
time_status = (txc->status & ~STA_RONLY) |
(time_status & STA_RONLY);
if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */
if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) {
result = -EINVAL;
goto leave;
}
time_freq = txc->freq - pps_freq;
}
if (txc->modes & ADJ_MAXERROR) {
if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) {
result = -EINVAL;
goto leave;
}
time_maxerror = txc->maxerror;
}
if (txc->modes & ADJ_ESTERROR) {
if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) {
result = -EINVAL;
goto leave;
}
time_esterror = txc->esterror;
}
if (txc->modes & ADJ_TIMECONST) { /* p. 24 */
if (txc->constant < 0) { /* NTP v4 uses values > 6 */
result = -EINVAL;
goto leave;
}
time_constant = txc->constant;
}
if (txc->modes & ADJ_OFFSET) { /* values checked earlier */
if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
/* adjtime() is independent from ntp_adjtime() */
if ((time_next_adjust = txc->offset) == 0)
time_adjust = 0;
}
else if ( time_status & (STA_PLL | STA_PPSTIME) ) {
ltemp = (time_status & (STA_PPSTIME | STA_PPSSIGNAL)) ==
(STA_PPSTIME | STA_PPSSIGNAL) ?
pps_offset : txc->offset;
/*
* Scale the phase adjustment and
* clamp to the operating range.
*/
if (ltemp > MAXPHASE)
time_offset = MAXPHASE << SHIFT_UPDATE;
else if (ltemp < -MAXPHASE)
time_offset = -(MAXPHASE << SHIFT_UPDATE);
else
time_offset = ltemp << SHIFT_UPDATE;
/*
* Select whether the frequency is to be controlled
* and in which mode (PLL or FLL). Clamp to the operating
* range. Ugly multiply/divide should be replaced someday.
*/
if (time_status & STA_FREQHOLD || time_reftime == 0)
time_reftime = xtime.tv_sec;
mtemp = xtime.tv_sec - time_reftime;
time_reftime = xtime.tv_sec;
if (time_status & STA_FLL) {
if (mtemp >= MINSEC) {
ltemp = (time_offset / mtemp) << (SHIFT_USEC -
SHIFT_UPDATE);
if (ltemp < 0)
time_freq -= -ltemp >> SHIFT_KH;
else
time_freq += ltemp >> SHIFT_KH;
} else /* calibration interval too short (p. 12) */
result = TIME_ERROR;
} else { /* PLL mode */
if (mtemp < MAXSEC) {
ltemp *= mtemp;
if (ltemp < 0)
time_freq -= -ltemp >> (time_constant +
time_constant +
SHIFT_KF - SHIFT_USEC);
else
time_freq += ltemp >> (time_constant +
time_constant +
SHIFT_KF - SHIFT_USEC);
} else /* calibration interval too long (p. 12) */
result = TIME_ERROR;
}
if (time_freq > time_tolerance)
time_freq = time_tolerance;
else if (time_freq < -time_tolerance)
time_freq = -time_tolerance;
} /* STA_PLL || STA_PPSTIME */
} /* txc->modes & ADJ_OFFSET */
if (txc->modes & ADJ_TICK) {
tick_usec = txc->tick;
tick_nsec = TICK_USEC_TO_NSEC(tick_usec);
}
} /* txc->modes */
leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0
|| ((time_status & (STA_PPSFREQ|STA_PPSTIME)) != 0
&& (time_status & STA_PPSSIGNAL) == 0)
/* p. 24, (b) */
|| ((time_status & (STA_PPSTIME|STA_PPSJITTER))
== (STA_PPSTIME|STA_PPSJITTER))
/* p. 24, (c) */
|| ((time_status & STA_PPSFREQ) != 0
&& (time_status & (STA_PPSWANDER|STA_PPSERROR)) != 0))
/* p. 24, (d) */
result = TIME_ERROR;
if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
txc->offset = save_adjust;
else {
if (time_offset < 0)
txc->offset = -(-time_offset >> SHIFT_UPDATE);
else
txc->offset = time_offset >> SHIFT_UPDATE;
}
txc->freq = time_freq + pps_freq;
txc->maxerror = time_maxerror;
txc->esterror = time_esterror;
txc->status = time_status;
txc->constant = time_constant;
txc->precision = time_precision;
txc->tolerance = time_tolerance;
txc->tick = tick_usec;
txc->ppsfreq = pps_freq;
txc->jitter = pps_jitter >> PPS_AVG;
txc->shift = pps_shift;
txc->stabil = pps_stabil;
txc->jitcnt = pps_jitcnt;
txc->calcnt = pps_calcnt;
txc->errcnt = pps_errcnt;
txc->stbcnt = pps_stbcnt;
write_sequnlock_irq(&xtime_lock);
do_gettimeofday(&txc->time);
notify_arch_cmos_timer();
return(result);
}
asmlinkage long sys_adjtimex(struct timex __user *txc_p)
{
struct timex txc; /* Local copy of parameter */
int ret;
/* Copy the user data space into the kernel copy
* structure. But bear in mind that the structures
* may change
*/
if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
return -EFAULT;
ret = do_adjtimex(&txc);
return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
}
inline struct timespec current_kernel_time(void)
{
struct timespec now;
unsigned long seq;
do {
seq = read_seqbegin(&xtime_lock);
now = xtime;
} while (read_seqretry(&xtime_lock, seq));
return now;
}
EXPORT_SYMBOL(current_kernel_time);
/**
* current_fs_time - Return FS time
* @sb: Superblock.
*
* Return the current time truncated to the time granuality supported by
* the fs.
*/
struct timespec current_fs_time(struct super_block *sb)
{
struct timespec now = current_kernel_time();
return timespec_trunc(now, sb->s_time_gran);
}
EXPORT_SYMBOL(current_fs_time);
/**
* timespec_trunc - Truncate timespec to a granuality
* @t: Timespec
* @gran: Granuality in ns.
*
* Truncate a timespec to a granuality. gran must be smaller than a second.
* Always rounds down.
*
* This function should be only used for timestamps returned by
* current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because
* it doesn't handle the better resolution of the later.
*/
struct timespec timespec_trunc(struct timespec t, unsigned gran)
{
/*
* Division is pretty slow so avoid it for common cases.
* Currently current_kernel_time() never returns better than
* jiffies resolution. Exploit that.
*/
if (gran <= jiffies_to_usecs(1) * 1000) {
/* nothing */
} else if (gran == 1000000000) {
t.tv_nsec = 0;
} else {
t.tv_nsec -= t.tv_nsec % gran;
}
return t;
}
EXPORT_SYMBOL(timespec_trunc);
#ifdef CONFIG_TIME_INTERPOLATION
void getnstimeofday (struct timespec *tv)
{
unsigned long seq,sec,nsec;
do {
seq = read_seqbegin(&xtime_lock);
sec = xtime.tv_sec;
nsec = xtime.tv_nsec+time_interpolator_get_offset();
} while (unlikely(read_seqretry(&xtime_lock, seq)));
while (unlikely(nsec >= NSEC_PER_SEC)) {
nsec -= NSEC_PER_SEC;
++sec;
}
tv->tv_sec = sec;
tv->tv_nsec = nsec;
}
EXPORT_SYMBOL_GPL(getnstimeofday);
int do_settimeofday (struct timespec *tv)
{
time_t wtm_sec, sec = tv->tv_sec;
long wtm_nsec, nsec = tv->tv_nsec;
if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
return -EINVAL;
write_seqlock_irq(&xtime_lock);
{
wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
set_normalized_timespec(&xtime, sec, nsec);
set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
time_adjust = 0; /* stop active adjtime() */
time_status |= STA_UNSYNC;
time_maxerror = NTP_PHASE_LIMIT;
time_esterror = NTP_PHASE_LIMIT;
time_interpolator_reset();
}
write_sequnlock_irq(&xtime_lock);
clock_was_set();
return 0;
}
void do_gettimeofday (struct timeval *tv)
{
unsigned long seq, nsec, usec, sec, offset;
do {
seq = read_seqbegin(&xtime_lock);
offset = time_interpolator_get_offset();
sec = xtime.tv_sec;
nsec = xtime.tv_nsec;
} while (unlikely(read_seqretry(&xtime_lock, seq)));
usec = (nsec + offset) / 1000;
while (unlikely(usec >= USEC_PER_SEC)) {
usec -= USEC_PER_SEC;
++sec;
}
tv->tv_sec = sec;
tv->tv_usec = usec;
}
EXPORT_SYMBOL(do_gettimeofday);
#else
/*
* Simulate gettimeofday using do_gettimeofday which only allows a timeval
* and therefore only yields usec accuracy
*/
void getnstimeofday(struct timespec *tv)
{
struct timeval x;
do_gettimeofday(&x);
tv->tv_sec = x.tv_sec;
tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
}
#endif
#if (BITS_PER_LONG < 64)
u64 get_jiffies_64(void)
{
unsigned long seq;
u64 ret;
do {
seq = read_seqbegin(&xtime_lock);
ret = jiffies_64;
} while (read_seqretry(&xtime_lock, seq));
return ret;
}
EXPORT_SYMBOL(get_jiffies_64);
#endif
EXPORT_SYMBOL(jiffies);
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